Telephone-exchange system.



B. G. DUNHAM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 20.1915- Pmmm Dec 4, 191?.

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BERT Gr. DUNHAM, 0F HAWTHORNE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNF IVIENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A. CORPORATION '01? NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed July 20, 1915.

To all whom it may concern:

Be it known that l, BERT G. DUNHAM, a. citizen of the United States, residing at Hawthorne, in the county of Passaic and State of New Jersey, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to circuit arrangements for selector switches employed in automatic telephone exchanges.

lhe object of this invention is .to provide a simple circuit arrangement for selector switches and to insure the proper selecting operation of such switches.

According to the main feature of this invention, an impulse receiving'mechanism, such as a line relay, serves the double purpose of first, receiving and transmitting the impulses sent from a substation or other sending position through an incoming line for controlling the selective operation of the switch, and second, this relay is used for testing the electrical condition of outgoing lines to which incoming lines may be on tended by the selector switch. By using a relay instead of an operating magnet for testing outgoing lines, the arresting of the selector switch is made more accurate.

Othernew and useful features of this invention will appear from the following detailed description and the appended claims.

The drawings represent diagrammatically a full automatic telephone exchange system, only so much being shown of the apparatus and circuits as is necessary for a clear understanding of this invention. The circuit and the mechanical construction of the apparatus employed in such telephone exchanges are well known to those skilled in the art, and therefore the following description will be restricted to the operation of a selector switch embodying the present invention.

The subscriber at substation 1 desiring to obtain a connection with substation 2 ,removes the receiver from the switch hook, causing thereby in the well-known manner a trunk finder or line switch 3 to extend the substation line to an idle trunk leading to a selector switch 4. Upon the seizure of an idle trunk by the brushes of the switch 3, a circuit is established from grounded battery Specification of Letters Patent.

Patented lDec. 4t, 191W.

Serial No. 40,834.v

5 through the left-hand winding of a line relay 6, wiper? of a side switch associated with selector 4, the calling incoming line and substation 1, sideswitch wiper 8 and the right-hand winding of line relay 6, to ground. Upon the encrgization of relay 6. a circuit is closed from ground through the armature and front contact of relay 6, sideswitch wiper 10, back contact and armature of a primary operating magnet 11 and the winding of a slow-acting escapement magnet 12, to grounded battery 13. Under the control of magnet 12 the wipers of the side switch are moved into their second position.

The subscriber at substation 1 proceeds now to send out impulses for setting selector switch t. By operating a calling device It provided at substation 1, short interruptions are produced in the calling lino circuit and therefore relay 6 becomes intermittently d3. energized and energized in accordance with the numberof interruptions produced in its circuit. Upon each release of the armature of relay 6, a circuit is closed from ground through the armature and back contact of this relay, side-switch wiper 15 and the winding of magnet 11, to grounded battery 16, and upon each energization of magnet 11 the brushes of selector 4: are stepped in a rotary direction to select the desired group of trunks or outgoing lines terminating at selector 4.

Release magnet 17 connected in parallel to the primary magnet 11 also received current impulses during the vibration of the armature of relay 6. Magnet 17 however, unlike magnet 11, is slow to pull up, and therefore the closure of its circuit (grounded battery 18, magnet 17 conductor 19, side-switch wiper 15, to ground at the armature of relay 6), for a short period does not cause its energization.

Upon the first release of the armature of line relay 6, a further circuit was. closed from ground through the armature and back contact of this relay, side-switch wiper 10 (in position 2), back contact and armature of magnet 11, and the winding of magnet 12, to grounded battery 13. Magnet 12 became energized and althoughduring the vibration of the armatures of relay 6 and magnet 11 its circuit wasinterrupted, due to its slowness to release, magnet 12 remained energized. In the second, third and lloh relay 6 maintains its armature attracted, thecircuit of the escapement magnet 12 is opened and the side-switch wipers are now moved into position 3. In this position of the side-switch wipers magnet 11 is disconnected and the circuit of relay 6 is opened at v side-switch wipers 7 and 8. Relay 6, however, ismaintained energized, a circuit being closed from ground through its righthand Winding, side-switch wiper 20, vertical off-normal contact 21 and the winding of magnet 11, to grounded battery 16. The current flowing through this circuit is insuliicient to cause the energization of magnet 11. After the sending out of impulses from substation 1, selector 4 will be caused to hunt for an idle outgoing line in the selected group of trunks. As is well known, the busy or idle condition of such outgoing lines or trunks is indicated by the connection of a certain battery potential to their multiple test terminals. In the present case the busy condition of a trunk is indicated by a grounded battery 22, connected through the winding of a release magnet 23, and a rotary olf-normal contact 24 to test terminal 25, and to the multiples of this terminal. Magnet 23 is slow to pull up and remains therefore deenergized during trunk hunting. The idle condition of a trunk is indicated by a ground connected through the armature and back contact of a line relay 26 and a side-switch wiper 27 to the test terminal 25 and'to the multiples of this terminal. The apparatus, by means of which the busy and idle test potentials are applied to the multipled terminal 25, are individual to a selector or connector switch 28. If the first set of terminals is busy, 2'. e. if selector 28 is in use, a circuit is closed from grounded battery 22 through the winding of magnet 23, contact 24 (closed when selector 28 is in an off-normal position), terminal 25, brush 29 of selector 4, side-switch wiper 20 and righthand winding of relay 6, to ground. Relay 6 remains energized and therefore a circuit is closed from ground through its armature and front contact, side-switch wiper 30 and back contact, armature and winding of a secondary operating magnet 31, to grounded battery 32. Magnet 31 becomes energized and causes the stepping of the brushes of selector 4 in a vertical direction to hunt for an idle trunk in the selected group. Upon the first vertical step taken by selector 4, contact 21 is opened and relay 6 receives e11- ergizing current over the test terminals of busy lines. Magnet 31 upon energization, interrupts at its back contact its circuit, and as long as it finds a circuit upon deenergization, causes the stepping of the selector. During the travel of the selector brushes from terminal to terminal, relay 6 is maintained energized, the interruptions produced in its circuit being of a very short duration. As soon as an idle trunk is reached, 0., to ihe test terminal of which ground is connected, relay 6 and therefore magnet 31 become deenergized. Upon the energization of relay 6, a circuit was closed from ground through the armature and front contact of relay 6, side-switchwiper 10, the back contact and armature of relay 11 and the winding of magnet 12 to grounded battery. Magnet 12 remains energized as long as relay 6 is energized. After an idle trunk has been. found and the armature of relay 6 is released, magnet 12 becomes deenergized and allows the side-switch wiper to escape into position 4, in which position the calling incoming line is extended through wipers 7 and 8, and through the brushes of selector 4 to an idle outgoing line leading to selector 28 adapted to coiiperate in the establishment of a connection between substations 1 and Upon the seizure of the idle trunk, relay 26 becomes energized and causes in the wellknown manner, under the control of substation 1, the operation of selector 28. Upon the energization of relay 26, the ground is disconnected from test terminal 25, and as soon as selector 28 leaves its normal position and contact 24 is closed, grounded battery is connected to the multiples of terminals 25 in order to prevent the seizure of this trunk by other selectors.

Upon the termination of the conversation the called subscriber at substation 2, by hanging up his receiver, causes, in the wellknown manner, the release of selector 28 and. the apparatus associated therewith. Upon the energization of magnet 23, a ground is connected to the conductor leading to terminal 25, and a circuit is closed, therefore, through brush 29 of selector 4, side-switch wiper 20, conductor 33, contact 34 (closed as soon as selector switch 4 leaves its normal position), and the winding of release magnet 17, to grounded battery 18. Magnet 17, upon. energization, closes a locking circuit for itself through its left-hand armature and front contact, contact 34 and its winding to grounded battery 18. Under the control of magnet 17, selector switch 4 and the associated side switch are restored to normal. the locking circuit of magnet 17 being closed until selector 4 reaches its normal position. 6., as long as contact 34 is closed. A fur ther result of the attraction of the lefthaud armature of magnet 17 is the sending of an impulse through conductor 33, terminal 35 and brush 36 of switch 3 to the releasing mechanism of this switch.

There is shown on the drawing connected to the right-hand armature of magnet 17 a condenser, a resistance and a grounded battery, which serve to prevent sparking at the operating contacts of relay 6 and magnets 11, 12, 17 and 31. Such anti-sparking devices are well known in the art and therefore a description of their operation does not seem necessary.

If the calling subscriber abandons the call by restoring his receiver to the switch hook prior to the sending out of impulses, relay 6 becomes de'e'nergized and closes a circuit from ground through its armature and back contact. side-switch wiper 15 (in position 2), and the winding of magnet 11, to grounded battery. Magnet 11 becomes energized and causes selector 1 to rotate one step, whereupon contact 3% is closed. Due tothe continuous closure of the circuit extending from ground through the armature and ack contact of relay 6, side-switch wiper 15, conductor 19 and the winding of release magnet 17, to grounded battery 18, this magnet becomes energized and causes the restoration of selector switch 4 and the as sociated side switch to normal. In the same manner as above described, magnet 17 closes a locking circuit for itself and remains energized until contact 341 is opened. Magnet 11 by attracting its armature prevents the energization of escapement magnet 12 upon 7 the release of the line relay armature.

If the call is abandoned at substation 1 during trunk huntmg, z. e., after the sending out of impulses, selector 4: continues its operation until an idle trunk is found, whereupon relay 6 and magnet 31 become de'e'nergized in the above described manner and magnet 1:2 causes the escapement of the side-switch wipers into position 4. Relay 26, however, due to the opening of its circuit at the calling substation 1, does not become energized and therefore a circuit is established from ground through the armature and back contact of relay 26 for release magnet 17 5 this magnet becomes energized and selector switch 1 is restored to normal.

If all the trunks terminating at selector switch 1- are found busy, the release of the selector switch and the associated mechanism is insured by the provision of a normally open contact so which is closed after the selector brushes have traversed the terminal bank of selector 1- in a vertical direction. A circuit is established thereupon from ground through the armature and front contact of relay 6, side-switch wiper 30, contact a0, conductor 33, contact 34, and the winding of magnet 17 to grounded battery 18. Magnet 17 becomes energized and causes the release of the selector in the above described man ner.

What is claimed is:

1. In a telephone exchange system, incoming lines and outgoing lines, a selector switch for extending an incoming line to an outgoing line, said selector switch having a primary and a secondary movement, a re lay operated by impulses sent over the incoming line for controlling the primary movement of said selector switch, and means controlled by said relay for testing the electrical condition of outgoing lines during the secondary movement of said selector switch.

2. In a telephone exchange system, incoming lines and outgoing lines, a selector switch for extending an incoming line to an outgoing line, said selectorswitch having a primary and a secondary movement, a relay operated by impulses sent over the in coming line for starting the primary movement of said selector switch, and means controlled by said relay for arresting the secondary movement of said selector switch.

8. In a telephone exchange system, incoming lines and outgoing lines, a selector switch for extending an incoming line to an outgoing line, said selector switch having a primary and a secondary movement, a relay operated by impulses sent over the incoming line for controlling the primary movement of said selector switch, and means associated with said outgoing lines for op erating said relay to control said secondary movement.

1. In a telephone exchange system, incoming lines and outgoing lines, a selector switch for extending an incoming line to an outgoing line, an impulse receiving mechanism, a primary and a secondary electromagnet for controlling the operation of said selector switch, means associated with incoming lines for causing said mechanism to control said primary electromagnet, and means associated with outgoing lines for operating said mechanism to control said secondary electromagnet.

5. In a telephone exchange system, incoming lines and outgoing. lines, a selector switch for extending an incoming line to an outgoing line, two electromagnets for successively controlling the operation of said selector switch, a relay for controlling said electromagnets, means controllable through incoming lines for causing said relay to opcrate one of said electromagnets, and means controllable through outgoing lines for operating said relay to operate the other of said electromagnets.

In witness whereof, I hereunto subscribe my name this 15th day of July, A. D. 1915.

BERT G. DUNHAM.

fiupies of this patent may be obtained for five cents each, by addressing? the Commissioner of Patents, Washington, I). (3. 

